1. Field of the Invention
The present invention relates generally to electronic devices such as Universal Serial Buss (USB) type devices for connecting various USB interface equipments, and, more particularly, to a structure of a contact point unit exposed through the surface of the casing of a USB-type connecting device.
2. Description of the Related Art
In recent years, USB-type interfaces (hereinafter referred to as "USB interfaces") have been employed as common interfaces for connecting various peripheral equipments, such as keyboard, mouse, and printer, to a personal computer.
In order to connect a plurality of USB interface peripheral equipments to a personal computer, a USB hub provided with a plurality of USB interface connectors is used.
In a USB interface, a cable made up of two signal lines and two power lines is used, so that power can be supplied to the peripheral equipments from each USB port via the USB hub.
FIG. 1 is a schematic view of the structure of a USB hub 1.
The USB hub 1 comprises a casing 2, a first USB port 3 formed by a USB connector disposed on the casing 2, second USB ports 4 formed by a plurality (four in FIG. 1) of USB connectors disposed on the casing 2, and a USB hub circuit 5 installed in the casing 2. The first USB port 3 is connected to the host of the USB hub circuit 5, and each of the second USB ports 4 is connected to the lower layer side of the USB hub circuit 5.
As shown in FIG.2, a personal computer 100 is connected to the first USB port 3, while a keyboard 6, a mouse 7, a printer 8, and a scanner 9, each of which is suitable for USB connection, are connected to the second USB ports 4.
With this structure, the keyboard 6, the mouse 7, the printer 8, and the scanner 9 can be used through the personal computer via the USB hub 1.
Furthermore, the USB hub 1 has a layer structure. Also, such a layer-structured USB hub can be connected by a hot-line connection (i.e., hot plugs). Thus, the usefulness of a personal computer can be increased further.
However, the USB hub 1 has disadvantages in that peripheral equipments are connected to the USB hub 1 via cables, and that the USB hub 1 is connected to a personal computer via a cable. Accordingly, a plurality of cables are required for the USB hub 1, and a large enough space for accommodating the cables is needed. Also, the arrangement of the cables becomes complicated.
To eliminate the above disadvantages, the USB hub 1 can be provided with a contact point unit exposed through the surface of the casing 2, so that the USB hub 1 can be connected to peripheral equipments without cables.
However, such an exposed contact point unit can be easily deformed by an inadvertent touch. When the contact point unit is not used, it is necessary to cover the contact point unit with a cap for protection, which only results in a higher cost.